MOSFET and IGBT Gate Driver With Negative Gate Pull-Down

Solution Overview

Problem

Power supply designs face high costs due to inefficiencies in transistor switching, leading to significant power losses during transient periods, which are not effectively reduced by existing technologies.

Innovation Solution

A gate driver integrated circuit with active pullup, pulldown, and grounding circuits that control the gate voltage of power transistors, using a negative voltage to speed up switching and reduce power losses by pulling the gate down to -15 volts during turn-off and back to zero volts before turn-on.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the switching frequency of the power supply is increased to reduce the size of magnetic components, then the size of magnetic components is reduced, but power loss during transient switching periods increases

Engineering Contradiction:

Improvesize of magnetic componentsVSAvoidpower loss during transient switching

Core Design Contradiction:

Volume of moving objectVSLoss of energy

Solution Approach 1:

The gate driver circuit performs preliminary action by pre-charging the gate capacitor to a negative voltage (e.g., -15V) before the actual switching event. This prepares the transistor for faster switching by reducing the voltage swing required during turn-on, thereby minimizing the time spent in the high-resistance transient state and reducing power loss during switching.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention implements dynamic gate driving by actively controlling the gate voltage through multiple stages: pre-charging to negative voltage, rapid charging to positive voltage during switching, and maintenance of gate voltage. This dynamic control optimizes the switching speed at different phases, reducing the duration of the transient high-resistance state and minimizing power loss while enabling higher switching frequencies.

Inventive Principle:

Principle #15Dynamics

2Ease of operation

If conventional gate driving is used to control transistor switching, then the transistor can be switched on and off, but significant power loss occurs during the transient non-conductive to conductive transition

Engineering Contradiction:

Improvetransistor switching controlVSAvoidpower loss during transient switching

Core Design Contradiction:

Ease of operationVSLoss of energy

Solution Approach 1:

The gate driver circuit performs preliminary action by pre-charging the gate capacitor to a negative voltage (e.g., -15V) before the actual switching event. This prepares the transistor for faster switching by reducing the voltage swing required during turn-on, thereby minimizing the time spent in the high-resistance transient state and reducing power loss during switching.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention implements dynamic gate driving by actively controlling the gate voltage through multiple stages: pre-charging to negative voltage, rapid charging to positive voltage during switching, and maintenance of gate voltage. This dynamic control optimizes the switching speed at different phases, reducing the duration of the transient high-resistance state and minimizing power loss while enabling higher switching frequencies.

Inventive Principle:

Principle #15Dynamics

3Loss of energy

If the transistor switching speed is increased to reduce transient power loss, then power loss during switching is reduced, but the complexity of the gate driver circuit increases

Engineering Contradiction:

Improvepower loss during transient switchingVSAvoidgate driver circuit complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The gate driver circuit is designed with multi-functionality to reduce complexity. The same circuit components and transistors are used for multiple purposes: the pull-up network serves both to charge the gate capacitor and to provide the negative pre-charge voltage, while the pull-down network handles both discharge and voltage maintenance. This universal use of components achieves fast switching and reduced power loss without proportionally increasing circuit complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The invention merges multiple functions into unified circuit blocks. The charge pump circuit is integrated within the gate driver, and the pull-up/pull-down networks are combined with the output stage transistors. This consolidation achieves the complex wave shaping and voltage control needed for fast switching while keeping the overall device complexity manageable through functional integration.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS10536145B2High-speed MOSFET and IGBT gate driver

Publication Date: 2020.01.14 LITTELFUSE INC

AI summary

A gate driver integrated circuit drives an output signal onto its output terminal and onto the gate of a power transistor. In a turn-on episode, a digital input signal transitions to a digital logic high level. In response, the gate driver integrated circuit couples the output terminal to a positive supply voltage terminal, thereby driving a positive voltage onto the gate of the power transistor. In response to a high-to-low transition of the digital input signal, the driver drives a negative voltage onto the output terminal and power transistor gate for a short self-timed period of time, and then couples the output terminal to a ground terminal, thereby driving the output terminal and power transistor gate up to ground potential. The output terminal and power transistor gate are then held at ground potential in anticipation of the next turn-on episode of the power transistor.